The present invention relates to composite cables that include at least one optical transmission component and at least one coaxial electrical transmission component.
Fiber optic cables include at least one optical fiber that can transmit data, computer, and telecommunication information. Composite cable designs combine the high bit-rate capacity of at least one optical fiber with the electrical transmission carrying capacity of at least one electrical conductor. Conventional composite cable designs, however, can have unacceptable optical/electrical performance characteristics, can require undesirable structural features that make optical fiber access difficult, can be difficult to route through cable passageways, and/or can make the cable expensive to produce.
For certain applications, a slotted core cable can be difficult to route through cable passageways and/or too expensive. For example, U.S. Pat. No. 5,777,260, incorporated by reference herein, discloses a coaxial cable having an optical ribbon disposed in a groove of a slotted core formed on the inner conductor of the coaxial cable. The groove proceeds helically with respect to the cable axis, and an outside envelope surrounds the slotted core.
Conventional composite cables can include electrical conductors that are sized for power, rather than data, transmission. For example, U.S. Pat. No. 4,867,527, incorporated by reference herein, discloses a combined electrical power and optical fiber cable. The cable requires a large electrical conductor with insulation therearound, a sheath around the insulation, a one or two-part protective layer around the insulation, a tube within the protective layer, and at least one optical fiber loosely received in the tube. The protective layer can have armoring therearound and, in this case, the radial thickness of the protective layer is from two to four times the diameter of the tube.
A relatively large and expensive conventional composite cable has been designed for undersea applications. U.S. Pat. No. 5,468,913, incorporated by reference herein, discloses an electro-optical marine tow cable requiring a relatively large bundle of coaxial core conductors positioned at the neutral axis of the cable with the coaxial shield conductor circumscribing a dielectric material. The dielectric material includes fiber optic transmitters helically circumscribing the core conductors. Surrounding the electro-optical assembly is a watertight jacket and a protective armor cover for carrying the tensile forces imparted to the cable during marine towing operations.
A composite cable can include cable components that make optical fiber access difficult. For example, U.S. Pat. No. 5,555,336, incorporated by reference herein, discloses a fiber optic power distribution cable including an optical fiber center, a first conductive layer coated around the optical fiber, an elongated glass capillary surrounding the optical fiber and a second conductive layer coated around the elongated glass capillary. As an additional example, U.S. Pat. No. 4,896,939, incorporated by reference herein, discloses a hybrid fiber optic/electrical cable and connector assembly. The cable includes a central optical fiber, a first tubular electrical conductor enclosing the optical fiber, a second tubular electrical conductor enclosing the first electrical conductor, and a dielectric support element disposed between the conductors for maintaining the conductors in a coaxial relationship.
It is an object of the present invention to provide a compact composite cable that is operative to transmit information in electrical and/or optical transmission modes, the cable preferably including an electrical coaxial conductor comprising an electrical conductor separated from a generally annular electrical conductor by a dielectric matrix, and at least one optical transmission component generally surrounded by the matrix.
It is an object of the present invention to provide a compact composite cable that is operative to transmit information in electrical and/or optical transmission modes, the cable preferably including an electrical conductor separated from a generally annular electrical conductor by a dielectric matrix; and at least one optical transmission component disposed in the matrix, the cable comprising stiffening members imparting a preferential bend characteristic and neutral axis thereto, the at least one optical fiber being generally aligned with the neutral axis.